"""
Dependency risk policy snapshot.

Loads the latest committed, read-only CVE / license / drift severity policy.
The policy never queries external CVE or license services, installs packages,
upgrades dependencies, writes lockfiles, builds images, pulls images, pushes
registries, calls paid APIs, creates shadow/canary traffic, or changes
production routing.
"""

from __future__ import annotations

import json
from pathlib import Path
from typing import Any

from src.services.snapshot_paths import default_evaluations_dir

_DEFAULT_EVALUATIONS_DIR = default_evaluations_dir(Path(__file__))
_SNAPSHOT_PATTERN = "dependency_risk_policy_*.json"
_SCHEMA_VERSION = "dependency_risk_policy_v1"


def load_latest_dependency_risk_policy(
    evaluations_dir: Path | None = None,
) -> dict[str, Any]:
    """Load the newest committed dependency risk policy snapshot."""
    directory = evaluations_dir or _DEFAULT_EVALUATIONS_DIR
    candidates = sorted(directory.glob(_SNAPSHOT_PATTERN))
    if not candidates:
        raise FileNotFoundError(f"no dependency risk policy snapshots found in {directory}")

    latest = candidates[-1]
    with latest.open(encoding="utf-8") as handle:
        payload = json.load(handle)

    if not isinstance(payload, dict):
        raise ValueError(f"{latest}: expected JSON object")
    _require_schema(payload, _SCHEMA_VERSION, str(latest))
    _require_read_only_boundaries(payload, str(latest))
    _require_operation_boundaries(payload, str(latest))
    _require_rollup_consistency(payload, str(latest))
    return payload


def _require_schema(payload: dict[str, Any], expected: str, label: str) -> None:
    actual = payload.get("schema_version")
    if actual != expected:
        raise ValueError(f"{label}: expected schema_version={expected}, got {actual!r}")


def _require_read_only_boundaries(payload: dict[str, Any], label: str) -> None:
    program_status = payload.get("program_status") or {}
    if program_status.get("read_only_mode") is not True:
        raise ValueError(f"{label}: program_status.read_only_mode must be true")

    boundaries = payload.get("approval_boundaries") or {}
    blocked_flags = {
        "sdk_installation_allowed",
        "paid_api_call_allowed",
        "shadow_or_canary_allowed",
        "production_routing_allowed",
        "destructive_operation_allowed",
    }
    allowed = sorted(flag for flag in blocked_flags if boundaries.get(flag) is not False)
    if allowed:
        raise ValueError(f"{label}: approval boundaries must remain false: {allowed}")


def _require_operation_boundaries(payload: dict[str, Any], label: str) -> None:
    boundaries = payload.get("operation_boundaries") or {}
    if boundaries.get("read_only_policy_allowed") is not True:
        raise ValueError(f"{label}: read_only_policy_allowed must be true")

    blocked_flags = {
        "external_cve_lookup_allowed",
        "external_license_lookup_allowed",
        "package_installation_allowed",
        "package_upgrade_allowed",
        "lockfile_write_allowed",
        "docker_build_allowed",
        "image_pull_allowed",
        "image_rebuild_allowed",
        "registry_push_allowed",
        "paid_api_call_allowed",
        "shadow_or_canary_allowed",
        "production_routing_allowed",
    }
    allowed = sorted(flag for flag in blocked_flags if boundaries.get(flag) is not False)
    if allowed:
        raise ValueError(f"{label}: operation boundaries must remain false: {allowed}")


def _require_rollup_consistency(payload: dict[str, Any], label: str) -> None:
    rules = payload.get("severity_rules") or []
    rollups = payload.get("rollups") or {}
    total = rollups.get("total_rules")
    if total != len(rules):
        raise ValueError(f"{label}: rollups.total_rules must equal severity_rules length")

    by_severity = rollups.get("by_severity") or {}
    for severity in ("critical", "high", "medium", "low"):
        actual = sum(1 for rule in rules if rule.get("severity") == severity)
        if by_severity.get(severity) != actual:
            raise ValueError(f"{label}: rollups.by_severity.{severity} must match rules")

    by_status = rollups.get("by_status") or {}
    for status in ("accepted", "action_required", "planned_next", "blocked"):
        actual = sum(1 for rule in rules if rule.get("status") == status)
        expected = by_status.get(status, 0)
        if expected != actual:
            raise ValueError(f"{label}: rollups.by_status.{status} must match rules")

    expected_by_status = {
        "action_required": set(rollups.get("action_required_rule_ids") or []),
        "planned_next": set(rollups.get("planned_next_rule_ids") or []),
        "accepted": set(rollups.get("accepted_rule_ids") or []),
    }
    for status, expected_ids in expected_by_status.items():
        actual_ids = {rule.get("rule_id") for rule in rules if rule.get("status") == status}
        if expected_ids != actual_ids:
            raise ValueError(f"{label}: rollups.{status}_rule_ids must match rules")
